Verification of Electron Beam Irradiation as a Lipid Decontamination
Method for Life Detection Instrumentation
Abstract
Lipids are key targets for current, proposed, and future life detection
missions to both rocky and icy worlds. With the high accuracy and low
limit of detection (LoD) required by many new and future instruments
(sub ~ppb range), decontamination of life detection
hardware, particularly components that handle or process planetary
samples in situ, is necessary to prevent false positives. Lipids are a
biosignature of interest as they are ubiquitous to all life as we know
it, can survive in the geologic record for an order of magnitude longer
than any other biomolecule (i.e. billions of years), and are able to
form through both biotic and abiotic processes. Traditional NASA
contamination control (CC) for life detection instruments primarily
focuses on hardware fabrication in sterile cleanroom environments,
killing of microbes, and flushing/mechanically removing contaminants off
instrument and spacecraft components. However, recent studies suggest
that standard cleaning methods are unlikely to sufficiently remove lipid
contaminants to meet instrument LoD. These include NASA-approved methods
for Planetary Protection (PP) (e.g., dry heat microbial reduction and
vapor phase H2O2) and cleanroom decontamination methods (e.g.,
protective clothing, HEPA air filtration, surface cleaning with
detergents/water/isopropyl alcohol, autoclave, ethylene oxide
treatment). Effective laboratory standard decontamination methods
(ashing at 550° C, chlorinated solvent flushes) are efficient at
eliminating lipid contamination, but are often incompatible with
sensitive materials required in the construction of life detection
instrument components. We will present the results of a study to
determine the efficiency of lipid decontamination using a
“nontraditional” CC method, Electron Beam Irradiation (EBI), that
would be compatible with common major instrument materials used in life
detection instrumentation. Percent lipid reduction following EBI
application will be compared to percent reduction following treatment
with traditional NASA PP methods, using standards from four classes of
lipid molecules that are proposed targets of life detection
instrumentation.